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<h1><a href="https://archiveofourown.org/works/24105478">Reverting the Alter</a> by <a class='authorlink' href='https://archiveofourown.org/users/Samwiches/pseuds/Samwiches'>Samwiches</a></h1>

<table class="full">

<tr><td><b>Category:</b></td><td>Fate/Grand Order, Fate/stay night &amp; Related Fandoms, Fate/stay night (Visual Novel)</td></tr>

<tr><td><b>Genre:</b></td><td>Alternate Universe, Beast Mode Sex, Biting, Creampie, Eventual Smut, F/M, Fate/stay night &amp; Related Fandoms References, Fluff and Smut, Groping, Inflation, Large Cock, Love, Mana Transfer, Marking, Master &amp; Servant, Master/Servant, Mild Smut, Nipple Licking, Orgasm, Sex, Smut, Vaginal Sex, Woman on Top</td></tr>

<tr><td><b>Language:</b></td><td>English</td></tr>

<tr><td><b>Status:</b></td><td>Completed</td></tr>

<tr><td><b>Published:</b></td><td>2020-05-10</td></tr>

<tr><td><b>Updated:</b></td><td>2020-05-10</td></tr>

<tr><td><b>Packaged:</b></td><td>2021-05-03 00:26:13</td></tr>

<tr><td><b>Rating:</b></td><td>Explicit</td></tr>

<tr><td><b>Warnings:</b></td><td>Creator Chose Not To Use Archive Warnings</td></tr>

<tr><td><b>Chapters:</b></td><td>1</td></tr>

<tr><td><b>Words:</b></td><td>1,858</td></tr>

<tr><td><b>Publisher:</b></td><td>archiveofourown.org</td></tr>

<tr><td><b>Story URL:</b></td><td>https://archiveofourown.org/works/24105478</td></tr>

<tr><td><b>Author URL:</b></td><td>https://archiveofourown.org/users/Samwiches/pseuds/Samwiches</td></tr>

<tr><td><b>Summary:</b></td><td><div class="userstuff">
              <p>Sam is my OC that has been couple with Cu in various stories -</p><p>Cu Chulainn was summoned as a Lancer unexpectedly to Samantha, by the corrupted ring of Magic above Fuyuki. After countless battles, betrayals, and his own distortion, he found he loved the damn woman. </p><p>In this short one shot, Cu's unsteady form brings about his Alter, and the only way to real him back to his original class is for Sam to effectively pass him a great deal of her pure mana. Being with the Berserker is anything but tame, and the transfer is dangerous since it involves having sex with the beast. Though, Sam loves every part of him, and will do whatever it takes to stabilize him, even if it's a "stretch".</p>
            </div></td></tr>

<tr><td><b>Relationships:</b></td><td>Cu chulainn - Relationship, Cú Chulainn Alter | Berserker/Original Character(s), Cú Chulainn | Lancer/Original Character(s), Lancer - Relationship, Lancer x OC</td></tr>

<tr><td><b>Kudos:</b></td><td>42</td></tr>

</table>

<a name="section0001"><h2>Reverting the Alter</h2></a>
<div class="story"><div class="fff_chapter_notes fff_head_notes"><b>Author's Note:</b><blockquote class="userstuff">
      <p>You know, for funsies.</p>
    </blockquote></div><div class="userstuff module">
    
    <p>This is unlike our usual sexcapades- was that fear? He had prepped me for this situation periodically but we both hoped it wouldn't come.</p><p> </p><p>The Cu Chulainn that was summoned to me was incomplete, a strange disarray of competing copies. The most discrete class changes were tolerable, and only had minor divergence in appearance.</p><p> </p><p>This version of him however.. well, it was a piece so broken it required special care to adjust him. Mana transfer would be best to collect his scattered thoughts and tackle his beastliness tendencies. Should I <em>survive</em> him.</p><p> </p><p>Practically pinned atop the bed, head leaning on the pillow for support: I did not resist his heavy hands pressing my bent upright thighs apart further. He parts them to make room for his monstrous part, and I press my eyes shut, weary of the penetration.</p><p> </p><p>However, nothing could prepare me for what was to infiltrate my lower folds his digits spread. My fingers find his wrists, agony ringing where his hand's grip has tightened into my skin. His piercing red eyes lock onto my emerald ones followed by a menacing grin curling onto his lips,</p><p> </p><p>"Be prepared to take it <em>all</em>", he said in a low growl, "I will ravish you."</p><p> </p><p>I swallow.</p><p> </p><p>Huge. Unnaturally huge. His tip was larger than my opening, and yet it still ventured inward against my body's futile resistance. I am slick from the sloppiness of his tongue and still, this pressure proving to be grueling.</p><p> </p><p>I launched forward into his chest, buckling from the pressure, desperately searching for support. My hands sprawl across his tan back as I inhale to fill my drained lungs. His grunts of satisfaction tickle my ear while he inches further in. Thankfully, there was some sort of control there. A hint of attachment. If not- I'd be warped from the ripping of my genitals as his other self feared.</p><p> </p><p>"Oh God's...it's so—"</p><p> </p><p>He would split me if he were to move to quick. My breath barely goes out as I try to speak, anything to distract me from the girth widening my walls beyond capacity.</p><p> </p><p>"Your tension only pleases me..." Pointed teeth clamped the crook of my neck and a moan escaped, the way his lips parted to let the tip of his tongue graze over the sensitive spot brought bumps to my skin.</p><p> </p><p>He bottoms out after a final, rough push and I had never been so <em>full. </em> Cu's regular forms were well endowed but this.. was an all new sensation. My breath barely broke free in a gasp while I desperately clawed at his skin for any sort of distraction.</p><p> </p><p>My body was in a spasm, physically attempting to handle the size. Peering down, I registered the irregular bulge in his shape and heave.  </p><p> </p><p>He drew his massive dick back. It was almost electrifying, and I scrape lines down his back,</p><p> </p><p>"Wait-" I say through jagged breaths, "Please, let... me adjust."</p><p> </p><p>An impractical growl had me quaking, his grip on my thighs deepening into my soft skin. His tail snared the sheets in its sideways thrash, hinting at aggression. A threat.</p><p> </p><p>My throat bobbed, but I stare down those deathly demonic eyes with my own piercing gaze. He needed to take the order. He answers by releasing my legs to pinch my nipple, and divert his attention to the opposite breast. He traces circles around the nub with his tongue, and clamped down with a tug. His groins sunk himself in me entirely yet again with a leveled push, releasing a strangely erotic moan from my small lips.</p><p> </p><p>"You take my cock well..." He groaned, yanking the black strands of hair that draped over my shoulder to arch my head back. His razor like fangs skimmed the tender area of my exposed throat, as his orbs track my response. Of course the idea of worry tried to press at my thoughts, but I knew this man was tempting me to show fear, and I of course refuse. </p><p> </p><p>I straddle him instead, to give him more of what he wants, that idle threat still lingering. I submerged his thickness in ever so close to the edge of my insides, a new form of pleasure swelling in my core. Man, to think I could actually <em>enjoy</em> being internally ruined like this was invigorating. </p><p> </p><p>Cu drew his dick slowly back a final time, and began his senseless pounding, patience gone.</p><p> </p><p>Frantically my hands palpated the muscles in his back. His jerks were anything but gentle, and it was a mixture of ecstasy and pain that filled my body to the brink. All the while the berseker's hands dragged markings down my curves. </p><p> </p><p>Those venturing hands stopped mid thigh to arch them back, aiding his magnificent thrusts deeper to the point I might black out. Crazy, to believe I now understood what it meant to be seeing stars, as he fucks me senseless. The way my pussy expands and engulfs the girth of his dick blurred the lines of pure erotica and utter madness.</p><p> </p><p>Cu's pounding slowed, as his cock threatened to force itself past the barrier deep within me. His groans of pleasure turn to low, rolling growls. I flinch at the irritation within as he attempts the impossible. I muster my inner strength and will myself to not be alarmed by the alter. My hands pat his back in a frenzy, attempting to halt his carnal desires.</p><p> </p><p>"Easy.. you can enjoy.. but do not break... okay...?" His thrusts slow, the head of his penis still threatening to enter, to <em>defile</em>, "You... would kill me..." I try to explain. For he would. His length and girth would shred my organs if he presses further. I lightly peck my lips against the center of his chest, trailing feathery kisses upwards to his chin.</p><p> </p><p>His lips smashed with mine and they parted, sliding my tongue with his. Cu's groans vibrated into my throat as his drilling of my cunt began again. It was odd, as his pushing was calculated, controlled, as if understanding my previous concerns.</p><p> </p><p>I did my best to mimic his thrusting with my own grinding, attempting to control how deep his cock dips. He slides his teeth across my lower lip and twists me around so my vision see the bed's headboard. With intensity, he stood, grappling with me as he pounded my tunnel vigorously and drags his tongue from base of my shoulder up to my ear. </p><p> </p><p>"Oh.. you'll... tear me...apart.." It was a small whimper, lacing with enjoyment. This new position had his girth expanding my lust to a whole different level.</p><p> </p><p>He gripps my tit firmly in his palm, his fingers yanking at the perk. Embarrassingly, shrill sounds exit my mouth from his hands rough fondling. His strokes then slow, and he grumbles almost incoherently,</p><p> </p><p>"Hmph.. I am.. being careful..."</p><p> </p><p>
  <em>Oh. Ha. That's cute.</em>
</p><p> </p><p>Sharp nails drag against my stomach, leaving imprints of red. In a quick turn so my stare was leveled with his own, my pussy was relieved of him. I wrap my arms behind his neck with a nod as he sat me onto him, my body contouring to his shape yet again.</p><p> </p><p>"Shiiiiiit," the words are almost inaudible, as it felt like all the air was sapped from my lungs at the immeasurable sensation in my loins yet again. Could I ever get used to his girth? Probably not, but hell, I sure as hell was enjoying it.</p><p> </p><p>My legs hug his torso and I dip my nails into him. My pussy devoured his dick whole, still with little ease. It was still so damn stimulating. Between the burn between my legs coupling that with flaring pleasure, he drills me so efficiently that my eyes roll.</p><p> </p><p>My pussy starts making sloppy sounds from the juices pouring out to support his senseless, endless stretching and strutting. He practically snarls, his hands sliding from my thighs to my ass cheeks that were ensnared in his powerful grip.</p><p> </p><p>"Heh, your cunt makes nice noises when I feed it my cock..." He jerks my midriff vehemently, and it took everything to continue holding on as I began to slip.</p><p> </p><p>With every thrust I was enamored, God's it was impossible. I felt myself clenching, that swollen bulge on my belly aching as his pace quickened. Despite all odds, I rode out my climax, focusing all my hips movement to draw out the release.</p><p> </p><p>"Ahh... your walls... they tighten on me.." Cu fusses, burrowing his face into the unmarked crease of my neck to sink his teeth into the tender flesh.</p><p> </p><p>A disastrous yelp exited my pathetic lips all the while encouraging him to yank my body down in uncontrollable, crashing waves.</p><p> </p><p>He shoves in hard, and i swear his dick thickened, the depth of his penetration so close- yet halted. I snuggle my head into his chest, and grip him so tight to my person as he finally releases.</p><p> </p><p>Gods, it fills and fills. I dare to look at the gorge of my ever expanding belly that I swear was to burst- but he delicately tilts my chin so i could meet his eyes instead,</p><p> </p><p>"Be still...do not tense..."</p><p> </p><p>A warning, or even... consulting? Fuck.. this was insane... I was locked in tight for his pooling cum to fill my womb with his seed.</p><p> </p><p>I feel lightheaded, my body in a tremor. My eyelids flutter, feeling the mana drain from me to fill him. He meticulously slips me off his softening piece and places me gently onto my back into the velvety sheets.</p><p> </p><p>There was satisfaction lingering in the aches where he nipped and scraped. My lower extremities sore from his feverish pounding. My vaginal muscles were quivering, trying to find their original form as his ejaculate leaked in bouts of a magical streams.</p><p> </p><p>My open palm cupped his cheek, as the shimmer of Cu Chulainn pulled back into his summoned Servant features.</p><p> </p><p>"Master... you..."</p><p> </p><p>My royal blue, rag tailed Lancer materialized his t-shirt and jeans to cloth himself. He ran his fingertips down my chest to my engorged belly that started to flatten out as more of his semen dripps from my lower gape.</p><p> </p><p>I leaned upward to brush my lips on his. I was alright, he did not harm me. The worry stained in those ruby eyes had my face burning with flush. I barely muster a whisper to concur again, I was not broken. I hover my hand over my abdominal muscles and sent a wave of magic to hasten the healing it was doing flawlessly on its own.</p><p> </p><p>His eyebrows furrow together, and his lip crooks up at the corner,</p><p> </p><p>"Tch, that simple, is it?"</p><p> </p><p>I try to laugh, but my consciousness began slipping. In my haze, I barely make out his attempting to piece together how he had not mangled me. Did his love spread across his varying classes? It was the only explanation his alter self showed restraint.</p><p> </p><p>Cu lifted me bridal style, mumbling something about cleaning me up. So I gave in to the drain of mana, drifting off into a space lulled by the sound of his harmonious heartbeat and complaints.</p>
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